As a quick test/demo, you could replace the contents of the file (/user/themes/landio/templates/partials/navigation.html.twig) with this text - where I have 'commented-out' the placement of the Login link:
Thanks Paul! It worked out. With your help I was able to find that spot in the navigation.html.twig
Today it was a bit frustrated... I think my page will be too complex for landio (I also need menus). But landio is beautiful. Do you have any tip for another/similar theme which would be easier for modification?
Great to hear you got things going @beginners_mind. Grav is quite different from many other CMSs, but I've been able to customize it far easier than many (mostly because of Twig and its really good design).
Paul, thanks for your kind support of my beginner questions.
I immeditley felt in love with grav. Some years ago I worked with Drupal, but I do not want to go back there...
I checked the skeletons again and I found "x-corporation" which would have one pop menu integrated. I am already quit far with landio: Do you think it would be a lot of work to add there a pop um menu?
You are most welcome @beginners_mind. Looking at that theme's skeleton it seems that the pages within the folder "05.Features" are the basis for the existing drop-down menu. By copying that folder and then editing the page (folders) within it should get you started.
BTW, a few other theme's also support dropdown menus in the Navbar, for example Bootstrap4 and my own Bootstrap4 Open Matter with Git Sync theme. Usually, you can find out if a theme supports that option by looking at its blueprint settings file, for example https://github.com/trilbymedia/grav-theme-bootstrap4/blob/develop/blueprints.yaml#L37
I do not know your theme requirements, but you might also want to take a look at the GitHub repo for themes of interest to see how much they are maintained etc if you are thinking of using the theme for a larger project etc.